The only way to ensure that is to teach them how it gets done. Not the dates and names and places (like 40s, Nazis/Jews, Germany), but the mechanics that turned reasonable people into sociopaths.

Our willingness to feel educated when we know only superficial details sets us up to miss the pattern when the details differ (like 2021, Vaxxed/Unvaxxed, Canada).

And once an ignorant person feels educated, they become a potent weapon against the truth.